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A079326
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a(n) = the largest number m such that if m monominoes are removed from an n X n square then an L-triomino must remain.
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17
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1, 2, 7, 9, 17, 20, 31, 35, 49, 54, 71, 77, 97, 104, 127, 135, 161, 170, 199, 209, 241, 252, 287, 299, 337, 350, 391, 405, 449, 464, 511, 527, 577, 594, 647, 665, 721, 740, 799, 819, 881, 902, 967, 989, 1057, 1080, 1151, 1175, 1249, 1274, 1351, 1377, 1457
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,2
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (1,2,-2,-1,1).
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FORMULA
| a(n) = (n^2)/2-1 (n even), (n^2-n)/2-1 (n odd).
a(n) = A204557(n-1) / (n-1). - Reinhard Zumkeller, Jan 18 2012
Contribution from Bruno Berselli, Jan 18 2011: (Start)
G.f.: x^2*(1+x+3*x^2-x^4)/((1+x)^2*(1-x)^3).
a(n) = n*(2*n+(-1)^n-1)/4-1.
a(n) = A105638(-n+2). (End)
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EXAMPLE
| a(3)=2 because if a middle row of 3 monominoes are removed from the 3 X 3, no L remains.
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CROSSREFS
| Cf. A093353, A104519.
Sequence in context: A042807 A005988 A199537 * A055673 A177737 A020895
Adjacent sequences: A079323 A079324 A079325 * A079327 A079328 A079329
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KEYWORD
| nonn,easy
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AUTHOR
| Mambetov Timur (timur_teufel(AT)mail.ru), Feb 13 2003
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EXTENSIONS
| Edited by Don Reble (djr(AT)nk.ca), May 28 2007
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